1. Field of the Invention
The present invention is in the field of prosthodontics and more specifically relates to an improved design for artificial teeth for use in complete and partial dentures.
2. Description of the Prior Art
With his natural teeth a man can exert over 100 pounds of chewing force comfortably. In the edentulous mouth the maximum pressure which can be exerted is on the average of only 15-20 pounds. For this reason, if artificial teeth are constructed in the same shape as the natural teeth, they will be grossly inadequate to perform the masticating function. Hence, anatomically formed teeth, while cosmetically correct, do not meet the functional requirements of artificial dentures. According to the studies of R. S. Manly ("Factors Affecting Masticatory Performance and Efficiency Among Young Adults", Journal of Dental Research, Vol. 30, p.p. 874-882, 1952) and K. Kapur and S. Soman, ("Masticatory Performance and Efficiency in Denture Wearers", Journal of Prosthetic Dentistry, Vol. 14, p.p. 687-694, 1964), the present denture teeth are about one sixth as efficient as natural teeth.
An article by I. R. Hardy in the Journal of Prosthetic Dentistry, Volume I, Nos. 1 and 2, page 14, January and March 1951, entitled "The Developments in the Occlusal Patterns of Artificial Teeth" surveyed the history of the development of nonanatomic teeth.
An early example of nonanatomic teeth were developed by F. A. French and described in "As We Progress; Why Modify Posterior Tooth Forms?" Dental Items of Interest, Vol. 57, pages 730-741, 1935. French wanted to use a monoplane concept and he also wanted to improve the efficiency and stability. He designed a monoplane tooth (the early design had a slight cusp rise on the maxillary teeth but a later version is completely flat) by removing the mandibular buccal half of the tooth. He placed an elevated narrow ridge of porcelain mesiodistally on the center and linqual of the mandibular occlusal surface. Later, the teeth were re-designed with the ridge of porcelain only in the center. The porcelain ridges however proved to be friable.
In 1946, Hardy, as further described in the above article, developed a serpentine-shaped cutting blade of metal, which extended across the occlusal surfaces of several teeth. These teeth were good for shredding but the blades were not long enough to provide efficient cutting. Dentures made with this blade could not be balanced (a dental term which means even contact of all teeth when the patient moves his jaw to other positions) because the serpentine pattern was flat, whereas teeth need to have a curved occlusal surface. Furthermore, these teeth were definitely not esthetic.
In an article in the Journal of Prosthetic Dentistry, Vol. 11, No. 1, pages 55-61, January-February 1961 entitled "Re-evaluation of Posterior Tooth Forms for Complete Dentures", M. B. Sosin described a blade mechanism technique he had developed, in which the entire occlusal surfaces of the maxillary first and second molars and second bicuspids were replaced by six bladed structures cast in a cobalt-chromium-molybdenum alloy. The structures are 8 millimeters in diameter and 4 millimeters in height.
These blades on the upper denture occupied the entire occlusal surface of the tooth, and were opposed by metal tables on the lower denture occupying its entire occlusal surface. As Sosin comments (page 56) ". . . esthetics is not a serious consideration." The teeth were, however, extremely efficient and functional. The technique described is very difficult and is not within the capabilities of the average dentist.
Thus it is clear from the prior art that there is a need for an artificial tooth that combines the efficient masticating capability of the "bladed" tooth with the esthetically pleasing appearance of the "anatomical" tooth, and also a need for a tooth that can be used by the average dentist, both in balanced and non-balanced occlusion, as both concepts are accepted by the dental profession.